‘Sex Change’ in Nature: Is This 5,000-Year-Old Tree Deciding It’s a Female After All?

Sex change: it’s a controversial topic even among humans. What about in plants, specifically among trees?

A roughly 3,000- to 5,000-year-old tree, the Fortingall Yew in Pertshire, seemed to have changed its mind about its gender recently. The UK’s oldest tree, which has been around since before the pyramids of Giza were erected, has been a male for centuries, according to records, but it is now manifesting female characteristics.

Dr. Max Coleman, a botanist at the Royal Botanic Garden in Ediburgh, was quite surprised to find “a group of three ripe red berries” in one branch of the ancient yew. The rest of the tree, however, was “clearly male.”

During spring and summer, it would be hard to determine the yew’s gender. But since it’s autumn in the UK, Dr. Coleman easily spotted the bright red berries that only female yews produce; males have spherical structures that release pollen.

To understand this phenomenon fully, let’s lay down the basics, shall we?

Gender in trees is complicated

Humans are either male or female, physiologically speaking. But when it comes to trees, gender is not that black and white.

A paper by Dr. Kim Coder of University of Georgia’s Warnell School of Forestry & Natural Resources lists down six sexual classifications of trees. Yes, trees have half a dozen genders! It’s a lot to take in, but, basically, trees either have the reproductive structures of both sexes or just one, either male or female.

Adding to the confusion is the fact that at least some trees can change gender. A change in gender can happen from season to season, over the life of a tree, or due to changes in the environment. For instance, a species of maple trees was observed to change its gender from male to female in what researchers believe was a strategy to grow its population that was negatively affected by reduced rainfall.

So, could the Fortingall Yew really be undergoing a sex change?

Nothing’s certain as of the moment. Scientists are studying the Fortingall berries to understand what’s happening to the ancient yew.

Dr. Coleman notes, however, that yew and some conifers have been observed to switch genders, so it’s definitely possible. But for the old yew, only one small branch has switched gender so far.

“It is possible that the Fortingall’s female flowers will spread, but it is unlikely that the whole tree will become female,” writes horticulturist Caroline Wright of Nottingham Trent University. “Female plants require more water and nutrients than males in order to produce their fruits and seeds. In an aging tree, a complete change would be a great source of stress. For an ancient gent like this one, that would probably be much more trouble than it was worth.”

What do you think of trees switching gender?

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Juvy is a freelance proofreader, copy editor and writer. A nice little nook with a good book would be ideal. But concocting plans for her next drawing or DIY project will suffice while she's still busy babysitting two daughters. Follow her on Twitter or connect with her on Google+.